In fact, the invention proposes to resolve the problem of improving the diffusion of sound through a small-sized timepiece. In fact, while the diffusion of sound is a simple matter in the case of pendulum clocks or clocks that have resonance spaces or cases of large dimensions designed to diffuse sound, it still poses a problem in the case of small-sized timepieces where the space for forming a resonant box or cavity is necessarily very limited and where numerous components impede the proper diffusion of the sound by damping it instead of amplifying it. This problem is all the more difficult since the sound sources provided in the form of bells, gongs or even keypads are themselves very small in size and since the level of sound amplification must be significant for the sound to be audible by the user and possibly the people around him. The amplification and diffusion of sound must not impair its purity and therefore it is vital to prevent any untimely resonance of another component of the timepiece.
Various attempts have been made to create resonant cavities that are generally operated from the user side, such as in the patent document JP 9 010 183 in the name of Seiko Epson, for example. However, the user himself assists in damping the vibration and the efficiency is quite limited because of this.
Tests aiming at using the crystal as vibrating element have long given mixed results. Patent application CH 8252 66 in the name of Spadini describes a flexible crystal rigidly mounted on the bezel and because it is made from an organic synthetic glass, the sound quality is generally greatly degraded because of the heterogeneity of the material.
Patent application FR 2 154 704 in the name of Timex describes an alarm watch with a piezoelectric oscillator that causes the watch crystal to resonate and is fastened directly thereto substantially perpendicular to the tangential plane of the crystal that is secured to the middle by a flexible ring of rubber or similar. This flexible arrangement absorbs too much energy to achieve the desired result. A vibration along the tangent plane to the crystal is only obtained with an oscillator generating vibrations in this direction.
The attachment of a crystal is known from document DE 198 23 981 in the name of Glassen, which describes a watch with a detachable crystal and an invisible edge clipped at its periphery onto a bezel. However, this is not provided for a striking or musical watch and is not designed for the diffusion of sound.
U.S. Pat. No. 4,115,994 describes a watch having a light source and a crystal arranged to diffuse the light in an optimum manner in association with reflection means at the dial.
Patent CH 626 497 in the name of Ebauches has broken new ground by enabling the crystal to be used as vibrating element to serve as vibration transmitter by interposing between the bezel and the crystal a thin annular connecting piece that absorbs little energy and does not impair the sound. These arrangements have been taken up by the patent EP 0 694 824 in the name of Asulab and by patent CH 698 742 in the name of Richemont, in which the annular piece assumes a profile of a dotted line. These solutions have the advantage of not deforming the sound and not significantly damping the vibrations, but the vibration amplitude of the crystal remains limited because of the peripheral hold thereof.
A patent CH 698 533 in the name of Richemont is also known that has sought a better transmission of sounds by attaching bells of a striking train directly to a crystal support welded thereto. Good transmission of the sound is assured, but the positioning of the bells is very specific, being under the crystal, and cannot be applied to all timepieces.